1. Field of the Invention.
The invention relates to a field of manipulating data stored in a memory and more specifically to shifting blocks of data stored in memory.
2. Prior Art.
There have been many graphics processors implemented in the past to process graphics data. A graphics processor must be capable of not only generating data, but also manipulating such data. Two typical operations involve rotation and shifting of video displays.
Normally a video display consists of raster lines having a number of pixels per line. A grouping of pixels, such as a 16.times.16 square, represents a character or a figure on the display. Each pixel information is represented by a bit (in a black and white display) or bits (in a color display). A 4-bit pixel will correspond to 16 shades of color.
A rotational operation allows a character to rotate on a display. This is useful when geometric figures need to be rotated. Prior art methods have used font tables in which all available characters are kept. The prior art method treated any rotated view of a character as a separate and unique character. Therefore, to provide 90, 180, and 270 degree rotation of a character, four fonts were necessary in the font table for each character.
A shifting operation allows a character to shift to a new position on a display. This is useful when a line or even a group of lines needs to be shifted to a new location. The prior art method employed a barrel shifting technique of shifting all bits a desired number of spaces.
The present invention describes a shifter which provides both a rotating and shifting operation to be performed in much faster time. Further, the invention provides for a manipulation of single word and multiple-word blocks of data.